Phosphorescent materials

ABSTRACT

Compounds comprising a ligand having a quinoline or isoquinoline moiety and a phenyl moiety, e.g., (iso)pq ligands. In particular, the ligand is further substituted with electron donating groups. The compounds may be used in organic light emitting devices, particularly devices with emission in the deep red part of the visible spectrum, to provide devices having improved properties.

The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.

FIELD OF THE INVENTION

The present invention relates to organic light emitting devices (OLEDs). More specifically, the present invention related to phosphorescent materials comprising a ligand having a quinoline or isoquinoline moiety and a phenyl moiety, e.g., (iso)pq ligands, which is further substituted with electron donating groups. These materials may provide devices having improved performance.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy)₃, which has the structure:

In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.

As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled in the art, a first “Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A “higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled in the art, a first work function is “greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a “higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

Compounds are provided having the formula:

M is a metal having an atomic weight higher than 40. L is an ancillary ligand. m is the oxidation state of the metal M. Preferably, M is Ir. n is at least 1. A is a fused carbocyclic or fused heterocyclic ring. Each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents. Each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Each R_(b) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. At least two R_(b) substituents are selected from the group consisting of alkoxy, aryloxy, alkyl amino, and aryl amino.

Preferably, L is a monoanionic bidentate ligand. More preferably, L is

and R_(x), R_(y), and R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Most preferably, at least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group. In one aspect, at least one of R_(x) and R_(y) is isobutyl. In another aspect, R_(z) is hydrogen.

In one aspect, the compound has a formula selected from the group consisting of:

In another aspect, the (iso)pq ligand is selected from the group consisting of:

Specific compounds are also provided. In particular, the compound is selected from the group consisting of Compound 1-Compound 7.

In one aspect, the compound has an emissive spectrum having a peak wavelength of about 650 nm to about 700 nm.

A first device comprising an organic light emitting device is also provided. The organic light emitting device further comprises an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer comprises a compound having the formula:

M is a metal having an atomic weight higher than 40. Preferably, M is Ir. L is an ancillary ligand. m is the oxidation state of the metal M. n is at least 1. A is a fused carbocyclic or fused heterocyclic ring. Each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents. Each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Each R_(b) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. At least two R_(b) substituents are selected from the group consisting of alkoxy, aryloxy, alkyl amino, and aryl amino.

Specific examples of devices comprising inventive compounds are provided. In one aspect, the compound used in the first device is selected form the group consisting of Compound 1-Compound 7.

The various specific aspects discussed above for Formula I are also applicable to a compound having Formula I when used in the first device. In particular, specific aspects of M, L, R_(a), R_(b), R_(x), R_(y), R_(z), and the (iso)pq ligand moiety of the compound having Formula I discussed above are also applicable to a compound having Formula I that is used in the first device.

In one aspect, the organic layer is an emissive layer and the compound having Formula I is an emitting dopant. In another aspect, the organic layer further comprises a host. Preferably, the host is a metal 8-hydroxyquinolate. More preferably, the host is:

In one aspect, the first device is a consumer product. In another aspect, the first device is an organic light emitting device.

In one aspect, the device comprises a compound having an emissive spectrum having a peak wavelength of about 650 nm to about 700 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

FIG. 3 shows an exemplary phosphorescent material comprising a quinoline or isoquinoline phenyl ligand further substituted with electron donating groups.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, and a cathode 160. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2. For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. patent application Ser. No. 10/233,470, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink jet and OVJD. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel displays, computer monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.).

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.

Using Ir(3-Meppy)₃ as a base structure, different alkyl substitution patterns on both the emitting ligand and the ancillary ligand have been previously studied to establish a structure-property relationship with respect to material processibility (evaporation temperature, evaporation stability, solubility, etc) and device characteristics of Ir(2-phenylquinoline) and Ir(1-phenylisoquinoline) type phosphorescent materials and their PHOLEDs. Alkyl substitutions are particularly important because they offer a wide range of tunability in terms of evaporation temperature, solubility, energy levels, device efficiency and narrowness of the emission spectrum. Moreover, they are stable functional groups chemically and in device operation when applied appropriately. Strong electron donating or electron withdrawing substituents on the emitting ligand can even further tune the emission energy of the complexes. In an effort to create phosphorescent emitters with very deep red emission, a variety of electron donating groups on the emitting ligand were studied to determine the extent of the red shifting effect.

The compounds provided herein exhibit very deep red emission in the range of 650 nm to 700 nm. Very deep red emission is useful for certain display applications requiring an emission wavelength between 650 nm and 700 nm. In particular, these compounds may be especially useful in OLED displays or other displays requiring very deep red emission.

The compounds disclosed herein comprise a ligand having an quinoline or isoquinoline moiety and a phenyl moiety, e.g., (iso)pq ligands. The (iso)pq ligand provides red emission. The phenyl moiety of the (iso)pq ligand is further substituted with electron donating groups, including alkoxy, aryloxy and amino groups. Without being bound by theory, it is believed that substitution of the (iso)pq ligand with electron donating groups causes further red shifting and, thus, very deep red emission.

Compounds are provided having the formula:

M is a metal having an atomic weight higher than 40. L is an ancillary ligand. m is the oxidation state of the metal M. Preferably, M is Ir. n is at least 1. A is a fused carbocyclic or fused heterocyclic ring. By fused, it is meant that A is a carbocyclic or heterocyclic ring that is fused to the pyridine ring of the phenyl pyridine moiety in the compound. A may be further substituted. Fusing A to the pyridine ring results in an (iso)pq ligand, as discussed above. Each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents. Each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Each R_(b) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. At least two R_(b) substituents are selected from the group consisting of alkoxy, aryloxy, alkyl amino, and aryl amino.

Preferably, L is a monoanionic bidentate ligand. More preferably, L is

and R_(x), R_(y), and R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Most preferably, at least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group. The α position refers to the first carbon that attaches to a functional group. In one aspect, at least one of R_(x) and R_(y) is isobutyl. In another aspect, R_(z) is hydrogen.

In one aspect, the compound has a formula selected from the group consisting of:

In another aspect, the (iso)pq ligand is selected from the group consisting of:

Specific compounds are also provided. In particular, the compound is selected from the group consisting of:

In one aspect, the compound has an emissive spectrum having a peak wavelength of about 650 nm to about 700 nm.

A first device comprising an organic light emitting device is also provided. The organic light emitting device further comprises an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer comprises a compound having the formula:

M is a metal having an atomic weight higher than 40. Preferably, M is Ir. L is an ancillary ligand. m is the oxidation state of the metal M. n is at least 1. A is a fused carbocyclic or fused heterocyclic ring, as discussed above. Each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents. Each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Each R_(b) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. At least two R_(b) substituents are selected from the group consisting of alkoxy, aryloxy, alkyl amino, and aryl amino.

Preferably, L is a monoanionic bidentate ligand. More preferably, L is

and R_(x), R_(y), and R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups. Most preferably, at least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group. In one aspect, at least one of R_(x) and R_(y) is isobutyl. In another aspect, R_(z) is hydrogen.

In one aspect, the compound has a formula selected from the group consisting of:

In another aspect, the (iso)pq ligand is selected from the group consisting of:

Specific examples of devices comprising inventive compounds are provided. In one aspect, the compound is selected from the group consisting of Compound 1-Compound 7.

In one aspect, the organic layer is an emissive layer and the compound having Formula I is an emitting dopant. In another aspect, the organic layer further comprises a host. Preferably, the host is a metal 8-hydroxyquinolate. More preferably, the host is:

In one aspect, the first device is a consumer product. In another aspect, the first device is an organic light emitting device.

In one aspect, the device comprises a compound having an emissive spectrum having a peak wavelength of about 650 nm to about 700 nm.

In addition, there are several other embodiments; however, these embodiments are less preferred.

A compound having the formula M(Li)_(m)(L′j)_(n) is provided. M is a metal having an atomic weight higher than 40. m is at least 1. n is at least 1. m+n is the oxidation state of the metal M. i is an indexing variable having a value from 1 to m. j is an indexing variable having a value from 1 to n. Each L independently has the formula:

A and B are each independently a 5 or 6-membered aromatic or heteroaromatic ring. A-B represents a bonded pair of aromatic or heteroaromatic rings coordinated to the metal via a nitrogen atom on ring A and an sp² hybridized carbon atom on ring B. Each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents. Each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl, or heteroaryl groups. Each R_(b) substituent is independently selected from a group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl, or heteroaryl groups, and at least one R_(b) substituent is selected from the group consisting of alkoxy, aryloxy, alkyl amino and arylamino. Each L′ independently has the formula:

R_(x), R_(y), R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl, or heteroaryl groups. At least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group. Preferably, at least one of R_(x) and R_(y) is isobutyl. Preferably, R_(z) is hydrogen.

In one aspect, the compound has the formula:

m is the oxidation state of the metal. m-n is at least 1.

In another aspect, the metal M is Ir.

In yet another aspect, the compound has a formula selected from the group consisting of:

In one aspect, the bonded pair of aromatic or heteroaromatic rings represented by A-B is selected from the group consisting of:

Specific non-limiting examples of such compounds include compounds selected from the group consisting of:

Additionally, a first device comprising an organic light emitting device is provided. The organic light emitting device comprises an anode, a cathode, and an organic layer, disposed between the anode and the cathode. The organic layer comprises a compound having the formula M(L_(i))_(m)(L′_(j))_(n). M is a metal having an atomic weight higher than 40. Preferably, the metal M is Ir. m is at least 1. n is at least 1. m+n is the oxidation state of the metal M. i is an indexing variable having a value from 1 to m. j is an indexing variable having a value from 1 to n. Each L independently has the formula:

A and B are each independently a 5 or 6-membered aromatic or heteroaromatic ring. A-B represents a bonded pair of aromatic or heteroaromatic rings coordinated to the metal via a nitrogen atom on ring A and an sp² hybridized carbon atom on ring B. Each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents. Each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl, or heteroaryl groups. Each R_(b) substituent is independently selected from a group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl, or heteroaryl groups. At least one R_(b) substituent is selected from the group consisting of alkoxy, aryloxy, alkyl amino and arylamino. Each L′ independently has the formula:

R_(x), R_(y), R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl, or heteroaryl groups. At least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group. Preferably, at least one of R_(x) and R_(y) is isobutyl. Preferably, R_(z) is hydrogen.

The various specific aspects discussed above for compounds having the formula M(L_(i))_(m)(L′_(j))_(n) are also applicable to a compound having the formula M(L_(i))_(m)(L′_(j))_(n) when used in the first device. In particular, specific aspects of M, L_(i), L′_(j), m, n, j, L, A, B, A-B, R_(a), R_(b), R_(x), R_(y), and R_(z) discussed above for compounds having the formula M(L_(i))_(m)(L′_(j))_(n) are also applicable to a compound having the formula M(L_(i))_(m)(L′_(j))_(n) when used in the first device.

Specific examples of compounds for use in the first device are provided. In one aspect, the compound is selected from the group consisting of Compound 1-Compound 11.

In one aspect, the organic layer is an emissive layer and the compound having Formula I is an emitting dopant. In another aspect, the organic layer further comprises a host. Preferably, the host is a metal 8-hydroxyquinolate. More preferably, the host is:

In one aspect, the device is a consumer product. In another aspect, the device is an organic light emitting device.

Combination with Other Materials

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present. The materials described or referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in embodiments of the present invention is not particularly limited, and any compound may be used as long as the compound is typically used as a hole injecting/transporting material. Examples of the material include, but not limit to: a phthalocyanine or porphryin derivative; an aromatic amine derivative; an indolocarbazole derivative; a polymer containing fluorohydrocarbon; a polymer with conductivity dopants; a conducting polymer, such as PEDOT/PSS; a self-assembly monomer derived from compounds such as phosphonic acid and sliane derivatives; a metal oxide derivative, such as MoO_(x); a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and a cross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, but not limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each Ar is further substituted by a substituent selected from the group consisting of hydrogen, deuterium, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, Ar¹ to Ar⁹ is independently selected from the group consisting of:

k is an integer from 1 to 20; X¹ to X⁸ is CH or N; Ar^(l) has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but not limit to the following general formula:

M is a metal, having an atomic weight greater than 40; (Y¹-Y²) is a bidentate ligand, Y1 and Y² are independently selected from C, N, O, P, and S; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and m+n is the maximum number of ligands that may be attached to the metal.

In one aspect, (Y¹-Y²) is a 2-phenylpyridine derivative.

In another aspect, (Y¹-Y²) is a carbene ligand.

In another aspect, M is selected from Ir, Pt, Os, and Zn.

In a further aspect, the metal complex has a smallest oxidation potential in solution vs. Fc⁺/Fc couple less than about 0.6 V.

Host:

The light emitting layer of the organic EL device in embodiments of the present invention preferably contains at least a metal complex as light emitting material, and may contain a host material using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complexes or organic compounds may be used as long as the triplet energy of the host is larger than that of the dopant.

Examples of metal complexes used as host are preferred to have the following general formula:

M is a metal; (Y³-Y⁴) is a bidentate ligand, Y³ and Y⁴ are independently selected from C, N, O, P, and S; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and m+n is the maximum number of ligands that may be attached to the metal.

In one aspect, the metal complexes are:

(O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, M is selected from Ir and Pt.

In a further aspect, (Y³-Y⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each group is further substituted by a substituent selected from the group consisting of hydrogen, deuterium, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl.

In one aspect, the host compound contains at least one of the following groups in the molecule:

R¹ to R⁷ are independently selected from the group consisting of hydrogen, deuterium, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

k is an integer from 0 to 20.

X¹ to X⁸ is selected from CH or N.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holes and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED.

In one aspect, compound used in HBL contains the same molecule used as host described above.

In another aspect, compound used in HBL contains at least one of the following groups in the molecule:

k is an integer from 0 to 20; L is an ancillary ligand, m is an integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable of transporting electrons. Electron transport layer may be intrinsic (undoped), or doped. Doping may be used to enhance conductivity. Examples of the ETL material are not particularly limited, and any metal complexes or organic compounds may be used as long as they are typically used to transport electrons.

In one aspect, compound used in ETL contains at least one of the following groups in the molecule:

R¹ is selected from the group consisting of hydrogen, deuterium, alkyl, alkoxy, amino, alkenyl, alkynyl, arylalkyl, heteroalkyl, aryl and heteroaryl, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

Ar¹ to Ar³ has the similar definition as Ar's mentioned above.

k is an integer from 0 to 20.

X¹ to X⁸ is selected from CH or N.

In another aspect, the metal complexes used in ETL contains, but not limit to the following general formula:

(O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N, N; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

In any above-mentioned compounds used in each layer of OLED device, the hydrogen atoms can be partially or fully deuterated.

In addition to and/or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exiton/hole blocking layer materials, electron transporting and electron injecting materials may be used in an OLED. Non-limiting examples of the materials that may be used in an OLED in combination with materials disclosed herein are listed in Table 1 below. Table 1 lists non-limiting classes of materials, non-limiting examples of compounds for each class, and references that disclose the materials.

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EXPERIMENTAL Compound Examples

Several of the compounds were synthesized as follows:

Example 1 Synthesis of Compound 1

Step 1. 2-chloroquinoline (9.0 g, 54.4 mmol), 3,5-dimethoxyphenylboronic acid (9.2 g, 59.8 mmol), Pd(PPh₃)₄ (1.8 g, 1.5 mmol), K₂CO₃ (22.4 g, 163 mmol), 1,2-dimethoxyethane (150 mL) and water (150 mL) were charged in a 500 mL round bottom flask. The reaction mixture was heated to reflux under nitrogen for 18 h. The reaction mixture was then cooled to ambient and the organic phase was separated from the aqueous phase. The aqueous phase was washed with ethyl acetate and all the organic components were combined and dried over anhydrous magnesium sulphate. The solvent was then removed under vacuum and the product was purified using silica gel chromatography (10% ethyl acetate in hexane as eluent). The material obtained was further purified by vacuum distillation to yield 12.2 g (95% yield) of product as a colorless oil.

Step 2. The ligand from Step 1 (16.54 g, 71 mmol), 2-ethoxyethanol (250 mL) and water (50 mL) were charged in a 1 L three-neck round bottom flask. Nitrogen gas was bubbled through the reaction mixture for 45 minutes. IrCl₃.3H₂O (5.0 g, 15 mmol) was then added and the reaction mixture was heated to reflux under nitrogen for 17 h. The reaction mixture was cooled to ambient temperature. Approximately half of the solvent was removed on the rotary evaporator and 200 mL of ethoxyethanol was added to the reaction mixture. The iridium dimer was not isolated and the reaction mixture was used as is for the following step.

Step 3. 2,8-dimethylnonane-4,6-dione (28 g, 152 mmol) and Na₂CO₃ (16 g, 152 mmol) were added to the dichlorobridged Iridium dimer solution from Step 2. The reaction mixture was stirred at room temperature for 48 h. The solvent was removed on the rotary evaporator and the crude dissolved in dichloromethane. The solution was passed through a 1 inch thick silica gel plug to remove and salts. The solution was removed and the crude was purified using silica gel chromatography with dichloromethane and hexanes as the mobile phase to give 8.0 g of product (73.5% yield).

Example 2 Synthesis of Compound 2

Step 1. 2-chloroquinoline (10.0 g, 61.3 mmol), 3-methoxyphenylboronic acid (9.2 g, 67.5 mmol), Pd(PPh₃)₄ (1.8 g, 1.5 mmol), K₂CO₃ (22.4 g, 163 mmol), 1,2-dimethoxyethane (150 mL) and water (150 mL) were charged in a 500 mL round bottom flask. The reaction mixture was heated to reflux under nitrogen for 18 h. The reaction mixture was then cooled to ambient temperature and the organic phase was separated from the aqueous phase. The aqueous phase was washed with ethyl acetate and all the organic components were combined and dried over anhydrous magnesium sulfate. The solvent was then removed under vacuum and the product was purified using silica gel chromatography (10% ethyl acetate in hexane as eluent). The material obtained was further purified by vacuum distillation to yield 13.0 g (90% yield) of product as a colorless oil.

Step 2. The ligand from Step 1 (10.0 g, 42.5 mmol), 2-ethoxyethanol (200 mL) and water (40 mL) were charged in a 1 L three-neck round bottom flask. Nitrogen gas was bubbled through the reaction mixture for 45 minutes. IrCl₃.3H₂O (4.0 g, 10.6 mmol) was then added and the reaction mixture was heated to reflux under nitrogen for 17 h. The reaction mixture was cooled to ambient temperature. Approximately half of the solvent was removed on the rotary evaporator and 200 mL of ethoxyethanol was added to the reaction mixture. The iridium dimer was not isolated and the reaction mixture was used as is for the following step.

Step 3. 2,8-dimethylnonane-4,6-dione (20 g, 108 mmol) and Na₂CO₃ (11.23 g, 106 mmol) were added to the dichlorobridged Iridium dimer solution from Step 2. The reaction mixture was stirred at room temperature for 48 h. The solvent was removed on the rotary evaporator and the crude dissolved in dichloromethane. The solution was passed through a 1 inch thick silica gel plug to remove and salts. The solution was removed and the crude was purified using silica gel chromatography with dichloromethane and hexanes as the mobile phase to give 5.0 g of product (52% yield).

Device Examples

All device examples were fabricated by high vacuum (<10⁻⁷ Torr) thermal evaporation. The anode electrode is 1200 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of LiF followed by 1000 Å of Al. All devices were encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H₂O and O₂) immediately after fabrication, and a moisture getter was incorporated inside the package.

The organic stack of the Device Example consisted of sequentially, from the ITO surface, 100 Å of hole injection layer (HIL), 300 Å of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD) as the hole transporting later (HTL), 300 Å of host (CBP or Compound D) doped with 9% of Compound 1-2 as the emissive layer (EML), and 400 Å of Alq₃ (tris-8-hydroxyquinoline aluminum) as the ETL.

As used herein, the following compounds have the following structures:

Particular emissive dopants for the emissive layer of an OLED are provided. These compounds may lead to devices having particularly good properties. The device structures are provided in Table 2, and the corresponding device data is provided in Table 3.

TABLE 2 VTE PHOLEDs Device Example HIL HTL EML(doping %) ETL Example 1 Compound C α-NPD Compound D Compound 1 Alq₃ (9%) Example 2 Compound C α-NPD Compound D Compound 2 Alq₃ (9%) Comparative Compound C α-NPD CBP Compound A Alq₃ Example 1 (9%) Comparative Compound C α-NPD Compound D Compound B Alq₃ Example 2 (9%)

TABLE 3 VTE Device data CIE At 1000 cd/m2 at J = 40 mA/cm2 Device λmax FWHM CIE CIE V LE EQE PE LE/ L₀, RT_(80%) Example (nm) (nm) (x) (y) [V] (cd/A) (%) (lm/W) EQE (cd/m²) (h) Example 1 672 81 0.71 0.29 15 1.1 5.8 0.2 0.2 546 60 Example 2 685 98 0.71 0.28 16.8 0.5 4.1 0.1 0.1 321 200 Comparative 622 62 0.67 0.33 8.1 19.9 18.9 7.7 1.1 6447 888 Example 1 Comparative 636 64 0.70 0.30 9.9 10.5 18.5 3.3 0.6 3408 799 Example 2

In particular, Device Examples 1 and 2 are significantly red shifted (>40 nm) from Comparative Example 1 and Comparative Example 2. This suggests that having 2 strong electron donating alkoxy groups compared to alkyl groups causes a marked reduction in the HOMO-LUMO gap, resulting in low energy emission in the deep red part of the visible spectrum.

It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore includes variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting. 

1. A compound having the formula:

wherein M is a metal having an atomic weight higher than 40; wherein L is an ancillary ligand; wherein m is the oxidation state of the metal M; wherein n is at least 1; wherein A is a fused carbocyclic or fused heterocyclic ring; wherein each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents; wherein each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups; wherein each R_(b) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups; and wherein at least two R_(b) substituents are selected from the group consisting of alkoxy, aryloxy, alkyl amino, and aryl amino.
 2. The compound of claim 1, wherein M is Ir.
 3. The compound of claim 1, wherein L is a monoanionic bidentate ligand.
 4. The compound of claim 1, wherein L is

and wherein R_(x), R_(y), and R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups.
 5. The compound of claim 1, wherein the compound has a formula selected from the group consisting of:


6. The compound of claim 5, wherein at least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group.
 7. The compound of claim 5, wherein at least one of R_(x) and R_(y) is isobutyl.
 8. The compound of claim 5, wherein R_(z) is hydrogen.
 9. The compound of claim 1, wherein the (iso)pq ligand is selected from the group consisting of:


10. The compound of claim 1, wherein the compound is selected from the group consisting of:


11. The compound of claim 1, wherein the compound has an emissive spectrum having a peak wavelength of about 650 nm to about 700 nm.
 12. A first device, comprising an organic light emitting device further comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, comprising a compound having the formula:

wherein M is a metal having an atomic weight higher than 40; wherein L is an ancillary ligand; wherein m is the oxidation state of the metal M; wherein n is at least 1; wherein A is a fused carbocyclic or fused heterocyclic ring; wherein each of R_(a) and R_(b) may represent mono, di, tri, or tetra substituents; wherein each R_(a) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups; wherein each R_(b) substituent is independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups; and wherein at least two R_(b) substituents are selected from the group consisting of alkoxy, aryloxy, alkyl amino, and aryl amino.
 13. The first device of claim 12, wherein M is Ir.
 14. The first device of claim 12, wherein L is a monoanionic bidentate ligand.
 15. The first device of claim 12, wherein L is

and wherein R_(x), R_(y), and R_(z) are each independently selected from the group consisting of hydrogen, deuterium, alkyl, heteroalkyl, aryl or heteroaryl groups.
 16. The first device of claim 12, wherein the compound has a formula selected from the group consisting of:


17. The first device of claim 16, wherein at least one of R_(x) and R_(y) contains a branched alkyl moiety with branching at a position further than the α position to the carbonyl group.
 18. The first device of claim 16, wherein at least one of R_(x) and R_(y) is isobutyl.
 19. The first device of claim 16, wherein R_(z) is hydrogen.
 20. The first device of claim 12, wherein the (iso)pq ligand is selected from the group consisting of:


21. The first device of claim 12, wherein the compound is selected from the group consisting of:


22. The first device of claim 12, wherein the organic layer is an emissive layer and the compound having Formula I is an emitting dopant.
 23. The first device of claim 22, wherein the organic layer further comprises a host.
 24. The first device of claim 23, wherein the hose is a metal 8-hydroxyquinolate.
 25. The first device of claim 23, wherein the host is:


26. The first device of claim 12, wherein the first device is a consumer product.
 27. The first device of claim 12, wherein the first device is an organic light emitting device.
 28. The first device of claim 12, wherein the compound has an emissive spectrum having a peak wavelength of about 650 nm to about 700 nm. 